The case for not being cruel to animals rests on the fact that this is not in the general human interest, not on the theory that animals have some inalienable natural rights. But the profit system prevents what is in the general human interest being applied.
The short answer is no. But, then, neither do humans.
The idea that humans have inalienable rights inherited from the "state of nature" which supposedly existed before they made a "social contract" to set up organised society is nonsensical. Humans have always been social animals. We wouldn't have become human if we hadn't been, since the main features which distinguish us from other animals—tool-making, abstract thought, speech— evolved, and could only have evolved, in and through society.
The suggestion that humans were once isolated individuals who later came together to set up society is logically absurd. How could humans have been in a position to negotiate a "social contract" if they hadn't first evolved the ability to think abstractly and speak, which presupposes that they already lived in society? But then this theory originated at a time—the 17th and 18th centuries—when the notion of evolution was unknown and nearly everybody believed that humans had been made in their fully developed form by an all-powerful god.
Revolution and the Rights of Man
All the same, the theory played an important role in history. It was the ideology of the rising class of capitalist entrepreneurs and traders and was used by them to pursue their struggle against the arbitrary rule of kings and aristocrats. If humans had innate rights which pre-existed society and the state, and which in fact it was the purpose of society and the state to protect and further, then if the state did not respect these rights humans were entitled to resist and overthrow it and establish one that did. This revolutionary implication of the doctrine of natural human rights was put to good propaganda use by those who led the American Revolution of 1776 and the French Revolution of 1789.
It is this aspect of the theory of natural rights that has attracted those opposed to the cruel treatment of animals. The theory that animals too have inalienable rights which ought to be respected provides a justification for their campaigns, including civil disobedience and in some cases violence and terrorism. But the theory that animals have natural rights is even more absurd than the theory that humans do.
Animals of course do exist in a "state of nature" and, while nature is not as "red in tooth and claw" as the popular myth has it, it is still true that some animals exist by killing and eating other animals. That is the way nature has evolved and is an integral part of all ecosystems. So how, in nature, can an animal be said to have a "right" not to be killed and eaten?
In fact, if "rights" were derived from behaviour in nature some animals could be said to have the "right" to kill other animals. And, since humans are animals that have always eaten meat why shouldn't they have the same "right" to kill and eat other animals? Or, if they are to be banned from this, are other animals too to be banned from killing other animals? Is the fox to be banned from eating the rabbit?
To be fair, many animal rights activists aren't interested in the philosophical position their name implies. Their message is much more simple and basic and derives more from the words of Elvis Presley than from Thomas Paine or Rousseau: Don't be cruel. But this is a message directed exclusively to humans and concerned only with the behaviour of humans towards other animals. In which case it would be sensible for them not to talk as if they thought that animals really do have inalienable natural rights, but to try to convince humans that it is not in the interests of humans to mistreat and be cruel to other animals.
Some animal rights theorists reject such an approach on the grounds that it is "anthropocentric" (human-centred) and leaves open the theoretical possibility of justifying the mistreatment of other animals if this could be shown to be in the general human interest. It is indeed a human-centred approach—this is why we are socialists: we want the best possible world for humans—but there is no reason why this should be at the expense of the suffering of other animals or why in practice it should lead to cruelty to animals being regarded as justified. It will, however, not rule out the conclusion that animals can be raised and killed for humans to eat, as long as this doesn't involve cruelty.
The case that maltreating animals is not in the general human interest could be made by underlining the following two points.
First, that animals, or at least those other animals that the debate is about (only a few eccentrics claim that insects have “rights"), are recognisably similar to us—they've got the same basic structure of a head, four limbs, two eyes, a nose, two ears, etc—and, like us, are more importantly sentient beings that can feel pain and show it. To tolerate the deliberate infliction of pain on them is to devalue opposition to human suffering too and so make it easier for some humans to get away with deliberately inflicting pain on other humans. In short, it is to help make for a less humane world.
Second, that animals raised under cruel conditions will not be healthy animals and so will not be good to eat, so defeating the whole purpose of humans raising them in the first place; which is to provide humans with nutritious food that contributes to them having a healthy life.
These are powerful arguments (which have led some socialists to be vegetarians and the rest of us trying to be careful about the food we eat). But if they are so powerful, why don't they prevail? Why do humans not act in their best interests but still mistreat animals?
Basically, it is because we live in a society where the overall human interest counts for little. We live in a class-divided society where it is the interest of the minority who own and control the means of production that prevails—and their interest, reflecting the economic logic of the system, is to increase their wealth by making profits.
Animals are abused because it is in the financial interest of those with money invested in meat production to produce as cheaply as possible, in order to remain competitive, even if this involves factory farming, battery-hens and caged veal calves. The rest of the owning class gain too, in terms of not having to pay higher wages and state benefits since the lower the cost of the meat the workers buy the less employers need to pay for their labour power, or the state for their subsistence.
There is no reason to doubt the sincerity of the farmers who say they dislike what happens to their calves after they've sold them, but that they have no alternative since they need to gain a living and that this provides a market for their products which enables them to keep their heads above water. It's not a question them being evil or immoral, but of what the economic system of production for sale on a market with a view to profit forces them to do.
It's the profit system that is the problem. It brings pressure to bear on economic decision-makers to opt for the cheapest methods of production on pain of being driven out of business altogether. If consideration of what is in the general human interest is to prevail, in this field of meat production as in all others, then the profit system must go. It must be replaced by a production-for-use system—which can only exist on the basis of the common ownership and democratic control of productive resources by the whole community.
In a genuinely socialist system of this kind cruelty to animals can be expected to stop as it would have no basis for occurring. The ending of the oppression and exploitation of humans by other humans—and the cruel treatment meted out as a matter of state policy by soldiers, police and prison guards (ask Amnesty for the full details)—will make humans generally less tolerant towards cruelty to other animals.
The vegetarians will of course be free to propagate their case, win recruits and pursue the diet of their choice, but most humans are obviously going to continue to eat some meat in the same way that humans as a species always have done. Humans evolved with the capacity to eat meat as well as vegetables and fruit, and it makes ecological sense to acquire some of our food (which is ultimately stored-up solar energy) in the form of meat, especially in winter times when locally-produced and so fresh vegetables are not available or of animals (like chickens, sheep and pigs) which can eat vegetation and scraps that we can't.
So, animals will be raised as food, but there will be no pressures to use methods of raising and slaughtering that impose suffering on them. The tyranny of the market and competitiveness will have gone and we'll be free to employ the most appropriate methods to produce the best quality meat—which implies treating the animals humanely.